GOP debate shows Donald Trump will not bow to political conventions

Donald Trump made his much-anticipated appearance at the first Republican presidential debate Thursday night - and he did not disappoint.

Trump accused one of the Fox News moderators of "living in the world of make-believe," called reporters "dishonest," described the Mexican government as "smarter" than its American counterparts in handling immigration issues and said many U.S. leaders are "stupid." He also said he was open to a third-party run against the eventual GOP nominee if he didn't like that person.

Donald Trump leads in current polls of the Republican field, but many top party donors, strategists and officials are very wary of his candidacy and believe he could never win a general election.

The mogul did little to allay those concerns in the first Republican debate. Trump brought his usual bombastic style to the debate, suggesting talk show host Rosie O'Donnell is fat and that he donated money to the Clinton Foundation in part to make sure the Clintons attended his wedding. And Trump's refusal to commit to backing the eventual GOP nominee, which means the businessman is leaving the door open to running as an independent, is likely to irritate further Republican Party leaders.

On policy, Trump and the other nine Republican candidates broke little ground. The businessman continued to suggest he would convince the Mexican government to build a border wall between the U.S. and Mexico, an idea experts suggest is implausible. Former Florida Gov. Jeb Bush repeated his proposal to create a pathway to legalization for undocumented immigrants, which Trump and several of the other Republican candidates oppose.

Kentucky Sen. Rand Paul and New Jersey Gov. Chris Christie continued their long-running disagreement about the controversial NSA bulk phone records collection program. Paul strongly opposes the program, which has now been limited, while Christie defended it.

The candidates agreed on most issues, repeatedly attacking the nuclear agreement the U.S and other world powers reached with Iran, highlighting what they viewed as flaws in Hillary Clinton's record and emphasizing their opposition to abortion.

Trump, was placed in the center of the 10 candidates on the stage because he is atop national polls, and there was much curiosity about how he would do in the debate, since the real-estate mogul has never run for elective office. His performance on Thursday was very similar to his two months as a candidate, a mix of conservative policy views, bragging about his business record and making politically-incorrect remarks.

Hear Trump's follow up comments on a possible third-party run on the Today Show​:

But if Trump was the same, the setting was much different. The debate has a much larger audience than most campaign events and will generate more media coverage. And the moderators repeatedly pressed Trump about moves he has made that contradict the conservatism he has expressed during the campaign, such as Trump's previous support for a European-style health care system and his campaign donations to Hillary Clinton and House Democratic Leader Nancy Pelosi.

Trump has surged in the polls over the last two months, in part because he was controlling the campaign narrative. He was drawing a disproportionate share of the media attention of the Republican primary and many voters did not know about the more liberal stands the mogul has taken or his openness to a third-party run.

Important performances for Rubio and Kasich. Both needed to show they can stand out and they did. Bush had a few stumbles but got stronger

The debate brought both more scrutiny to Trump's record and more attention to his rivals. Now, the question will be if Trump can sustain his polling advantage in the midst of this changing environment.

The debate also suggested Trump is not going to tone down his style to appease to the Republican establishment. This should be a relief for his rivals. The Republican Party is very unlikely to nominate a person who speaks as bluntly as Trump.

CLEVELAND, OH - AUGUST 06: Republican presidential candidates (L-R) Wisconsin Gov. Scott Walker, Donald Trump and Jeb Bush take the stage for the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)

CLEVELAND, OH - AUGUST 06: Republican presidential candidates (L-R) New Jersey Gov. Chris Christie, Sen. Marco Rubio (R-FL), Ben Carson, Wisconsin Gov. Scott Walker, Donald Trump, Jeb Bush, Mike Huckabee, Sen. Ted Cruz (R-TX) and Sen. Rand Paul (R-KY) take the stage for the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Scott Olson/Getty Images)

CLEVELAND, OH - AUGUST 06: Republican presidential candidates (L-R) Ben Carson, Wisconsin Gov. Scott Walker, Donald Trump and Jeb Bush take the stage for the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Scott Olson/Getty Images)

CLEVELAND, OH - AUGUST 06: Republican presidential candidates (L-R) Jeb Bush, Mike Huckabee, Sen. Ted Cruz (R-TX), Sen. Rand Paul (R-KY) and John Kasich take the stage for the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)

CLEVELAND, OH - AUGUST 06: Republican presidential candidates (L-R) Wisconsin Gov. Scott Walker, Donald Trump and Jeb Bush participate in the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)

CLEVELAND, OH - AUGUST 06: Republican presidential candidate New Jersey Gov. Chris Christie participates in the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)

CLEVELAND, OH - AUGUST 06: Audience members are reflected in a window as Republican presidential candidates (L-R) New Jersey Gov. Chris Christie, Sen. Marco Rubio (R-FL), Ben Carson, Wisconsin Gov. Scott Walker, Donald Trump, Jeb Bush, Mike Huckabee, Sen. Ted Cruz (R-TX), Sen. Rand Paul (R-KY) and John Kasich participate in the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)